The invention relates generally to chiller refrigeration systems and, more particularly, to a method of individually controlling inlet guide vanes at an inlet of a compressor of the chiller refrigeration system.
In many conventional chillers, the compressor, such as a centrifugal compressor for example, is driven by a driving means, such as an electric motor for example, either directly or through a transmission. Optimum performance of the compressor is strongly influenced by the rotating speed of the compressor. The volume of refrigerant flowing through the compressor must be adjusted for changes in the load demanded by the air conditioning requirements of the space being cooled. Control of the flow is typically accomplished by varying the inlet guide vanes and the impeller speed, either separately or in a coordinated manner.
When a conventional chiller system is initially started, the inlet guide vanes assembly is typically arranged in a fully closed position, allowing only a minimum amount of flow into the compressor to prevent the motor from stalling. Once the motor is operating at a maximum speed, the inlet guide vanes are rotated together to a generally open position based on the flow entering into the compressor. Conventional inlet guide vane assemblies includes a set of vanes, such as 7 or 11 vanes for example, connected by a cable to a group of idler and drive pulleys. The drive pulleys of the assembly are actuated by a motor coupled to the drive pulleys through a drive chain. The complex mechanical system for adjusting the position of the inlet guide vanes is labor intensive to manufacture and prone to assembly errors. In addition, because of the complex connection between an actuator and the vanes, the inlet guide vane assembly is slow to respond to an adjustment thereof.